Open-circuit purging method and device for fuel cell system and storage medium

Abstract

An open-circuit purging method for a fuel cell system. The fuel cell system comprises a stack (4) and a DC-DC module (5), and the method comprises: when the fuel cell system is shut down, on the basis of an under-voltage protection voltage of the stack (4), determining a first target value of a low-side current, wherein the low-side current is a current output by the stack (4) to the DC-DC module (5), and the first target value is greater than 0 A; purging the stack on the basis of the first target value, and acquiring the current voltage of the stack (4); when the current voltage is discharged to the under-voltage protection voltage, controlling the DC-DC module (5) to discharge the current voltage to a safe voltage of the stack, and determining a second target value of the low-side current, wherein the second target value is 0 A; and purging the stack on the basis of the second target value.

Description

Open-circuit purging method, equipment and storage medium for fuel cell systems

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application No. 2024114424953, filed on October 16, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of fuel cell technology, and in particular to an open-circuit purging method, apparatus and storage medium for a fuel cell system. Background Technology

[0004] As a major automobile producer, China boasts a huge car market. While automobiles bring economic benefits, they also involve significant energy consumption and environmental pollution. With increasingly fierce competition in the automotive sector, various companies and universities have begun researching vehicles equipped with fuel cell systems.

[0005] The fuel cell system consists of a stack and a DC-DC module. The stack generates electricity through a chemical reaction, while the DC-DC module, connected to the stack, steps up and down the output voltage to meet the vehicle's power requirements. When the fuel cell system shuts down, it first performs a closed-circuit purging process, followed by an open-circuit purging process, to remove some of the water from the stack and maintain its moisture content within a suitable range.

[0006] Currently, during open-circuit purging, the current output from the fuel cell stack to the DC-DC module (i.e., the low-side current of the DC-DC module) is mostly a fixed value of 0A. This causes the fuel cell stack voltage to remain at a high potential, which not only damages the fuel cell stack structure but also poses a high-voltage safety hazard, leading to malfunctions in the fuel cell system. Summary of the Invention

[0007] This disclosure provides an open-circuit purging method, apparatus, and storage medium for a fuel cell system, thereby at least partially solving the problem that fuel cell systems are prone to failure during open-circuit purging.

[0008] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.

[0009] According to a first aspect of the present disclosure, an open-circuit purging method for a fuel cell system is provided. The fuel cell system includes an interconnected fuel cell stack and a DC-DC module. The method includes: when the fuel cell system is shut down, determining a first target value of a low-side current based on an undervoltage protection voltage of the fuel cell stack, wherein the low-side current is the current output from the fuel cell stack to the DC-DC module, and the first target value is greater than 0A; purging the fuel cell stack based on the first target value; and acquiring the current voltage of the fuel cell stack.

[0010] When the current voltage is discharged to the undervoltage protection voltage, the DC-DC module is controlled to discharge the current voltage to the safe voltage of the fuel cell stack, and a second target value of the low-side current is determined, wherein the second target value is 0A; and the fuel cell stack is purged according to the second target value.

[0011] According to a second aspect of the present disclosure, an open-circuit purging device for a fuel cell system is provided, including a processor and a memory, wherein the memory stores computer program instructions executable by the processor, and when the processor executes the computer program instructions, it implements the steps of the method described in any of the first aspects above.

[0012] According to a third aspect of the present disclosure, a computer-readable storage medium is provided, the computer-readable storage medium storing computer program instructions that, when executed by a processor, cause the processor to perform the steps of the method as described in any of the first aspects above.

[0013] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0014] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0015] Figure 1 shows a schematic diagram of a fuel cell system according to some embodiments of the present disclosure;

[0016] Figure 2 shows a schematic flowchart of an open-circuit purging method for a fuel cell system according to some embodiments of the present disclosure;

[0017] Figure 3 shows a block diagram of an open-circuit purging apparatus for a fuel cell system according to some embodiments of the present disclosure;

[0018] Figure 4 shows a schematic diagram of the structure of an open-circuit purging device for a fuel cell system according to some embodiments of the present disclosure.

[0019] Explanation of reference numerals in the attached diagram: 1-Air subsystem; 2-Hydrogen subsystem; 3-Thermal management subsystem; 4-Stack; 5-DC-DC module; 100-Air filter; 101-Air flow meter; 102-Air compressor; 103-Intercooler; 104-Humidifier; 105-Back pressure valve; 106-Stack inlet shut-off valve; 107-Stack outlet shut-off valve; 108-Bypass valve; 201-Hydrogen circulation pump; 202-Proportional valve; 203-Hydrogen inlet valve; 301-Water pump; 302-Thermostatic valve; 303-Heat dissipation device; 601-Gas-liquid separator; 602-Drain valve; 603-Nitrogen venting valve; 604-Mixer. Embodiments of the present invention

[0020] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure.

[0021] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0022] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0023] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily need to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0024] It should also be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such uses of these terms can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described.

[0025] To enable those skilled in the art to better understand this disclosure, a brief description of the fuel cell system involved in this disclosure will first be given with reference to Figure 1.

[0026] Figure 1 shows a schematic diagram of a fuel cell system according to some embodiments of the present disclosure. As shown in Figure 1, in some embodiments, the fuel cell system includes an air subsystem 1, a hydrogen subsystem 2, a thermal management subsystem 3, a fuel cell stack 4, and a DC-DC module 5, etc. The air subsystem 1 may include an air filter 100, an air flow meter 101, an air compressor 102, an intercooler 103, a humidifier 104, a back pressure valve 105, a stack inlet shut-off valve 106, a stack outlet shut-off valve 107, and a bypass valve 108. The air filter 100, air flow meter 101, air compressor 102, intercooler 103, humidifier 104, back pressure valve 105, stack inlet shut-off valve 106, and the inlet of the cathode of the fuel cell stack 4 are sequentially connected. The outlet of the cathode of the fuel cell stack 4 is connected to the stack outlet shut-off valve 107. The bypass valve is used to connect the air subsystem to the environment. When the inlet shut-off valve 106 in the air subsystem 1 is open, the flow rate of air entering the cathode of the fuel cell stack 4 can be adjusted by the air compressor 102 and the back pressure valve 105. The hydrogen subsystem 2 may include a hydrogen circulation pump 201, a proportional valve 202, and a hydrogen inlet valve 203. The hydrogen inlet valve 203, the proportional valve 202, and the anode inlet of the fuel cell stack 4 are connected in sequence. The hydrogen inlet valve 203, the proportional valve 202, the anode inlet of the fuel cell stack 4, and the anode outlet of the fuel cell stack 4 form a hydrogen circuit. The hydrogen circulation pump is installed in the hydrogen circuit. When the hydrogen inlet valve 203 in the hydrogen subsystem 2 is open, the flow rate and pressure of hydrogen entering the anode of the fuel cell stack 4 can be adjusted by the proportional valve 202 and the hydrogen circulation pump 201. The thermal management subsystem 3 may include a water pump 301, a temperature control valve 302, and a heat dissipation device 303. The thermal management subsystem 3 has a cooling circuit for cooling the fuel cell stack. The water pump 301, temperature control valve 302, and heat dissipation device 303 are installed in the cooling circuit. The flow direction of the coolant in the cooling circuit can be controlled by the temperature control valve 302, and the temperature and flow rate of the coolant entering and leaving the fuel cell stack 4 can be controlled by the water pump 301 and the heat dissipation device 303 (e.g., a cooling fan). These three subsystems provide the fuel cell stack with suitable temperature, oxygen, and hydrogen according to the power requirements of the vehicle control unit. The fuel cell stack 4 generates electricity through a chemical reaction between oxygen and hydrogen. The DC-DC module 5 is used to step up and down the voltage output from the fuel cell stack 4 to meet the power requirements of the entire vehicle.

[0027] It should be noted that the components of the air subsystem 1, hydrogen subsystem 2, thermal management subsystem 3, and fuel cell stack 4 can be connected by compatible pipes.

[0028] In related technologies, the low-side current of the DC-DC module is 0A during open-circuit purging, which presents several problems: First, because the stack voltage discharge is not considered, the stack voltage cannot be discharged quickly, posing a high-voltage safety hazard; second, the stack voltage remains at a high potential, which can damage the stack's lifespan; third, residual air inside the fuel cell system is not consumed, and after shutdown, the oxygen in the stack continues to consume the hydrogen, resulting in a negative hydrogen pressure differential, which can damage the stack structure. These problems can easily lead to fuel cell system failures. This embodiment addresses this issue by controlling the low-side current to a first target value during stack purging, discharging the stack voltage to the undervoltage protection voltage, and then using the DC-DC module to discharge the stack voltage to a safe voltage. This ensures that the stack voltage is discharged completely after the fuel cell system shuts down, preventing the stack voltage from remaining at a high potential and reducing the failure rate of the fuel cell system.

[0029] Figure 2 shows a schematic flowchart of an open-circuit purging method for a fuel cell system according to some embodiments of the present disclosure. As shown in Figure 2, in some embodiments, the open-circuit purging method for the fuel cell system can be applied to the above-described fuel cell system, and the method may include the following steps:

[0030] Step 201: When the fuel cell system is shut down, determine the first target value of the low-side current based on the undervoltage protection voltage of the fuel cell stack, wherein the low-side current is the current output from the fuel cell stack to the DC-DC module, and the first target value is greater than 0A.

[0031] Step 202: Purge the fuel cell stack according to the first target value and obtain the current voltage of the fuel cell stack;

[0032] Step 203: When the current voltage is discharged to the undervoltage protection voltage, control the DC-DC module to discharge the current voltage to the safe voltage of the fuel cell stack, and determine a second target value for the low-side current, wherein the second target value is 0A; and,

[0033] Step 204: Purge the fuel cell stack according to the second target value.

[0034] Understandably, after a fuel cell system is shut down, it is typically necessary to first perform closed-circuit purging with a large low-side current, followed by open-circuit purging with a 0A low-side current, to expel some of the water inside the stack and maintain the water content within a suitable range. In this embodiment, the low-side current is controlled in stages during open-circuit purging after the fuel cell system is shut down.

[0035] First, the initial target values ​​for different undervoltage protection voltages and low-side currents can be calibrated. Then, based on the undervoltage protection voltage of the fuel cell stack (e.g., 60V), the corresponding initial target value for the low-side current is determined by looking up a table. This initial target value is relatively small, but greater than 0A, for example, 10A. The fuel cell stack is then purged using the initial target value to discharge the current voltage of the stack.

[0036] When the current voltage of the fuel cell stack reaches the undervoltage protection voltage, the DC-DC module performs the undervoltage protection function. At this time, the second target value of the low-side current of the DC-DC module is set to 0A, the voltage discharge is stopped, the fuel cell stack is purged at 0A, and the discharge relay in the DC-DC module is controlled to close, so as to discharge the current voltage to the safe voltage of the fuel cell stack (e.g., 35V).

[0037] During the purging process, the hydrogen subsystem and the air subsystem can also be controlled synchronously.

[0038] In some embodiments, the hydrogen inlet valve, proportional valve, drain valve, and nitrogen vent valve can be controlled to close to stop the hydrogen supply to the stack anode.

[0039] In some embodiments, the speed of the air compressor can be controlled according to the target purging flow rate of the fuel cell stack; the opening degree of both the inlet shut-off valve and the outlet shut-off valve can be controlled to reach the maximum opening degree; and the opening degree of the back pressure valve can be controlled according to the ambient temperature.

[0040] Understandably, the target air flow rate can be set based on the target purge flow rate of the fuel cell stack. The higher the target purge flow rate, the higher the target air flow rate. Then, the compressor speed is controlled in a closed loop based on the target air flow rate. The opening degree of the back pressure valve can be obtained from a table based on the ambient temperature. The lower the ambient temperature, the smaller the opening degree of the back pressure valve. At this time, the air pressure entering the stack will be higher, which can improve the purging intensity.

[0041] Since the hydrogen supply to the anode of the fuel cell stack has stopped, the hydrogen will be depleted, and the current voltage of the fuel cell stack will decrease accordingly.

[0042] In some embodiments, the fuel cell purging phase can be terminated when the current voltage is less than a third preset value (e.g., 10V).

[0043] This embodiment of the invention, when the fuel cell system is shut down, determines a first target value for the low-side current based on the undervoltage protection voltage of the fuel cell stack. The low-side current is the current output from the fuel cell stack to the DC-DC module, and the first target value is greater than 0A. The fuel cell stack is then purged according to the first target value, and the current voltage of the stack is acquired. If the current voltage is discharged to the undervoltage protection voltage, the DC-DC module is controlled to discharge the current voltage to the safe voltage of the fuel cell stack, and a second target value for the low-side current is determined, where the second target value is 0A. The fuel cell stack is then purged according to the second target value. This technical solution can prevent the fuel cell stack voltage from remaining at a high potential state during open-circuit purging of the fuel cell system, thus reducing the failure rate of the fuel cell system.

[0044] It should be noted that the above embodiments describe the steps for purging the fuel cell stack during open-circuit purging. The purpose of the fuel cell stack purging stage is to stop the hydrogen supply to the anode of the fuel cell stack. During the purging stage, air from the air subsystem can be introduced into the fuel cell stack by controlling the components of the cathode and the air subsystem, thereby discharging some of the water inside the fuel cell stack and bringing the water content inside the fuel cell stack within a set range.

[0045] In addition to the stack purging stage, open-circuit purging can also include component purging and cooling purging stages. The purpose of the component purging stage is to remove residual liquid water from the components of the air and hydrogen subsystems. The purpose of the cooling purging stage is to control the components of the thermal management subsystem to rapidly reduce the inlet temperature of the coolant to below 40°C, thereby liquefying the water vapor in the fuel cell system and removing residual liquid water from the components of the fuel cell system through purging.

[0046] After the fuel cell stack purging phase is completed, the infeed shut-off valve and the outfeed shut-off valve are closed, and the bypass valve is opened to prevent air from entering the fuel cell stack. At the same time, the purged liquid water and air are discharged from the fuel cell system, and the current voltage of the fuel cell stack will increase. At this time, in order to further reduce the amount of water generated by hydrogen consuming oxygen in the fuel cell stack after the fuel cell system is shut down, and to shorten the duration of the high potential of the fuel cell stack, a low current control strategy can be adopted during the component purging phase.

[0047] In some embodiments, during the component purging phase, a third target value for the low-side current can be determined based on the current voltage; the components of the hydrogen subsystem and the air subsystem are purged based on the third target value, wherein the third target value is less than the first target value.

[0048] During the implementation process, if the current voltage is less than the first preset value, the third target value is determined to be 0A; if the current voltage is greater than the second preset value, the third target value is determined to be a value between 0A and the first target value; wherein the second preset value is greater than the first preset value.

[0049] Taking a first preset value of A1 and a second preset value of A1+10A as an example, if the current voltage is less than A1, the third target value is set to 0A. If the current voltage is greater than A1+10A, the third target value is set to a value between 0A and the first target value (e.g., 5A) to reduce the current voltage below A1. If the current voltage is between A1 and A1+10A, the third target value remains unchanged. This second preset value design avoids frequent fluctuations in the low-side current, improving control stability.

[0050] In some embodiments, during the component purging stage, the opening of the hydrogen inlet valve, drain valve, and nitrogen purging valve can be controlled; the duty cycle of the proportional valve can be controlled according to the target hydrogen pressure; and the speed of the hydrogen circulation pump can be controlled to the minimum speed. The duty cycle of the proportional valve can be obtained through closed-loop control based on the target hydrogen pressure.

[0051] In some embodiments, during the component purging stage, the speed of the air compressor can be controlled according to the ambient temperature; the infeed shut-off valve, the outfeed shut-off valve, and the back pressure valve can be controlled to close; and the opening degree of the bypass valve can be controlled to reach the maximum opening degree.

[0052] The speed of the air compressor can be set according to the ambient temperature. The lower the ambient temperature, the higher the possibility of water remaining in the parts freezing, which requires increasing the purging flow rate. Therefore, the higher the target purging flow rate, the higher the speed of the air compressor.

[0053] Understandably, closing the infeed and outfeed valves can prevent air from entering the fuel cell stack and reacting with hydrogen to produce water; by controlling the opening of the bypass valve to its maximum, water and air blown out of the components can be quickly discharged.

[0054] During the component purging phase, residual liquid water in the components is blown away by low current control. When the low current control time reaches the upper limit, that is, when the duration of the component purging phase reaches the preset duration, the fuel cell control unit can send a shutdown command to the DC-DC module to stop the low current control and end the component purging phase.

[0055] By implementing low-current control during the component purging stage, the current voltage of the fuel cell stack can be reduced to below a first preset value, which can further reduce the amount of water produced by subsequent hydrogen oxygen consumption, while shortening the duration of high potential and improving the lifespan of the fuel cell stack.

[0056] In some embodiments, during the cooling and purging phase, the opening degree of the temperature control valve can be controlled to reach the maximum opening degree; the speed of the water pump can be controlled to the rated speed of the water pump; and the speed of the cooling fan can be controlled to the rated speed of the cooling fan.

[0057] Understandably, since the DC-DC module is shut down during the component purging phase, no current control strategy is involved during the cooling purging phase. By controlling the opening of the temperature control valve to its maximum, the cooling loop of the thermal management subsystem can be switched to a large-circulation mode, rapidly reducing the coolant inlet temperature. By controlling the water pump speed to its rated speed, heat can be quickly removed through a large flow rate, rapidly reducing the coolant inlet temperature. By setting the speed of the heat dissipation device to its rated speed, the heat dissipation rate of the cooling loop in the large-circulation mode can be accelerated.

[0058] During the cooling and purging phase, the control strategies for the air subsystem and hydrogen subsystem remain consistent with those during the component purging phase, and will not be elaborated further here.

[0059] By controlling the components of the thermal management subsystem during the cooling purging phase of the open-circuit purging process, the inlet temperature of the coolant is rapidly reduced to a specified value. This liquefies the water vapor in the fuel cell system before purging, preventing the condensate from freezing inside the fuel cell system due to the condensation of residual water vapor caused by the decrease in internal temperature, thus avoiding the failure of the fuel cell system to start up.

[0060] This embodiment of the invention purges the components of the fuel cell stack and fuel cell system at different stages and at different coolant inlet temperatures, improving the purging effect, removing residual liquid water from the stack and components, and preventing the fuel cell system from failing to start.

[0061] The following describes an embodiment of the apparatus disclosed herein, which can be used to perform the open-circuit purging method for the fuel cell system described in the above embodiments of this disclosure. For details not disclosed in the apparatus embodiments of this disclosure, please refer to the embodiments of the open-circuit purging method for the fuel cell system described above.

[0062] Referring to Figure 3, a block diagram of an open-circuit purging device for a fuel cell system according to some embodiments of the present disclosure is shown. As shown in Figure 3, the open-circuit purging device for a fuel cell system according to an embodiment of the present disclosure includes: a first current determination module 301, used to determine a first target value of the low-side current based on the undervoltage protection voltage of the fuel cell stack when the fuel cell system is shut down, wherein the low-side current is the current output from the fuel cell stack to the DC-DC module, and the first target value is greater than 0A; a first purging module 302, used to purge the fuel cell stack according to the first target value and obtain the current voltage of the fuel cell stack; a second current determination module 303, used to control the DC-DC module to discharge the current voltage to the safe voltage of the fuel cell stack when the current voltage is discharged to the undervoltage protection voltage, and to determine a second target value of the low-side current, wherein the second target value is 0A; and a second purging module 304, used to purge the fuel cell stack according to the second target value.

[0063] In some embodiments of this disclosure, based on the foregoing scheme, the open-circuit purging device of the fuel cell system further includes a hydrogen subsystem control module (not shown in the figure) for controlling the closure of the hydrogen inlet valve, proportional valve, drain valve and nitrogen discharge valve.

[0064] In some embodiments of this disclosure, based on the foregoing scheme, the open-circuit purging device of the fuel cell system further includes an air subsystem control module (not shown in the figure), which is used to control the speed of the air compressor according to the target purging flow rate of the fuel cell stack; control the opening degree of both the inlet shut-off valve and the outlet shut-off valve to reach the maximum opening degree; and control the opening degree of the back pressure valve according to the ambient temperature.

[0065] In some embodiments of this disclosure, based on the foregoing scheme, the open-circuit purging device of the fuel cell system further includes a component purging module (not shown in the figure), used to determine a third target value of the low-side current based on the current voltage; and to purge the components of the hydrogen subsystem and the air subsystem based on the third target value; wherein the third target value is less than the first target value.

[0066] In some embodiments of this disclosure, based on the foregoing scheme, the component purging module is further configured to determine a third target value of 0A when the current voltage is less than a first preset value; and to determine a third target value between 0A and the first target value when the current voltage is greater than a second preset value; wherein the second preset value is greater than the first preset value.

[0067] In some embodiments of this disclosure, based on the foregoing scheme, the component purging module is also used to control the opening of the hydrogen inlet valve, the drain valve, and the nitrogen discharge valve; control the duty cycle of the proportional valve according to the target hydrogen pressure; and control the speed of the hydrogen circulation pump to the minimum speed.

[0068] In some embodiments of this disclosure, based on the foregoing scheme, the component purging module is also used to control the speed of the air compressor according to the ambient temperature; control the infeed shut-off valve, the outfeed shut-off valve and the back pressure valve to close; and control the opening degree of the bypass valve to reach the maximum opening degree.

[0069] In some embodiments of this disclosure, based on the foregoing scheme, the open-circuit purging device of the fuel cell system further includes a cooling purging module (not shown in the figure) for controlling the opening degree of the temperature control valve to reach the maximum opening degree;

[0070] The water pump speed is controlled to the rated speed of the water pump; the cooling fan speed is controlled to the rated speed of the cooling fan.

[0071] Based on the same inventive concept, this disclosure also provides an open-circuit purging device for a fuel cell system. Referring to FIG4, a schematic diagram of the structure of the open-circuit purging device for a fuel cell system in this disclosure is shown. The open-circuit purging device for a fuel cell system includes one or more memories 404, one or more processors 402, and at least one computer program (computer program instruction) stored in the memory 404 and executable on the processor 402. When the processor 402 executes the computer program, it implements the method described above.

[0072] In Figure 4, a bus architecture (represented by bus 400) is shown. Bus 400 may include any number of interconnected buses and bridges, linking various circuits including one or more processors represented by processor 402 and memory represented by memory 404. Bus 400 may also link various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further herein. Bus interface 405 provides an interface between bus 400 and receiver 401 and transmitter 403. Receiver 401 and transmitter 403 may be the same element, i.e., a transceiver, providing a unit for communicating with various other devices over a transmission medium. Processor 402 is responsible for managing bus 400 and general processing, while memory 404 can be used to store data used by processor 402 during operation.

[0073] Based on the same inventive concept, this disclosure provides a computer-readable storage medium storing computer program instructions that, when executed by a processor, cause the processor to perform the steps of the method described above.

[0074] Based on the same inventive concept, this disclosure provides a computer program product, including a computer program, which, when executed by a processor, causes the processor to perform the steps of the method described above.

[0075] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored as one or more instructions or codes on or transmitted via a computer-readable medium. Other examples and embodiments are within the scope and spirit of this disclosure and the appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hardwired, or any combination thereof. Furthermore, the functional units may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit.

[0076] In the several embodiments provided in this disclosure, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between units or modules may be electrical or other forms.

[0077] The units described as separate components may or may not be physically separate. Similarly, the components of the control device may or may not be physical units; they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0078] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this disclosure, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this disclosure. The aforementioned storage medium includes various media capable of storing computer program instructions, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0079] In this disclosure, when the fuel cell system is shut down, a first target value for the low-side current is determined based on the undervoltage protection voltage of the fuel cell stack. The low-side current is the current output from the fuel cell stack to the DC-DC module, and the first target value is greater than 0A. The fuel cell stack is then purged according to the first target value, and the current voltage of the stack is acquired. If the current voltage is discharged to the undervoltage protection voltage, the DC-DC module is controlled to discharge the current voltage to the safe voltage of the fuel cell stack, and a second target value for the low-side current is determined, where the second target value is 0A. The fuel cell stack is then purged according to the second target value. This technical solution can prevent the fuel cell stack voltage from remaining at a high potential state during open-circuit purging of the fuel cell system, thereby reducing the failure rate of the fuel cell system.

[0080] The above description is merely an embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of the claims of this disclosure.

Claims

1. An open-circuit purging method for a fuel cell system, the fuel cell system comprising an interconnected fuel cell stack and a DC-DC module, the method comprising: In the event of a shutdown of the fuel cell system, a first target value for the low-side current is determined based on the undervoltage protection voltage of the fuel cell stack, wherein the low-side current is the current output from the fuel cell stack to the DC-DC module, and the first target value is greater than 0A. The fuel cell stack is purged according to the first target value, and the current voltage of the fuel cell stack is obtained; If the current voltage is discharged to the undervoltage protection voltage, the DC-DC module is controlled to discharge the current voltage to the safe voltage of the fuel cell stack, and a second target value for the low-side current is determined, wherein the second target value is 0A; and, The fuel cell stack is purged according to the second target value.

2. The open-circuit purging method of a fuel cell system according to claim 1, wherein, The fuel cell system further includes a hydrogen subsystem, which includes a hydrogen inlet valve, a proportional valve, a drain valve, and a nitrogen venting valve. The method further includes: The hydrogen inlet valve, the proportional valve, the drain valve, and the nitrogen discharge valve are controlled to close.

3. The open-circuit purging method of a fuel cell system according to claim 2, wherein, The fuel cell system further includes an air subsystem, which includes an air compressor, a stack inlet shut-off valve, a stack outlet shut-off valve, and a back pressure valve. The method further includes: The speed of the air compressor is controlled according to the target purging flow rate of the fuel cell stack; The opening degree of both the infeed shut-off valve and the outfeed shut-off valve is controlled to reach the maximum opening degree; The opening degree of the back pressure valve is controlled according to the ambient temperature.

4. The open-circuit purging method of a fuel cell system according to claim 1, wherein, The fuel cell system further includes a hydrogen subsystem and an air subsystem. After purging the fuel cell stack according to the second target value, the method further includes: A third target value for the low-side current is determined based on the current voltage; wherein the third target value is less than the first target value; The components of the hydrogen subsystem and air subsystem are purged according to the third target value.

5. The open-circuit purging method of a fuel cell system according to claim 4, wherein, Determining the third target value of the low-side current based on the current voltage includes: If the current voltage is less than the first preset value, the third target value is determined to be 0A; If the current voltage is greater than the second preset value, the third target value is determined to be a value between 0A and the first target value; wherein the second preset value is greater than the first preset value.

6. The open-circuit purging method for a fuel cell system according to claim 4, wherein, The hydrogen subsystem includes a hydrogen inlet valve, a proportional valve, a drain valve, a nitrogen venting valve, and a hydrogen circulation pump. The method further includes: Control the opening of the hydrogen inlet valve, the drain valve, and the nitrogen discharge valve; The duty cycle of the proportional valve is controlled according to the target hydrogen pressure; The speed of the hydrogen circulation pump is controlled to the minimum speed.

7. The open-circuit purging method for a fuel cell system according to claim 4, wherein, The air subsystem includes an air compressor, a reactor inlet shut-off valve, a reactor outlet shut-off valve, a back pressure valve, and a bypass valve. The method further includes: The speed of the air compressor is controlled according to the ambient temperature; Control the infeed shut-off valve, the outfeed shut-off valve, and the back pressure valve to close; and, Control the opening degree of the bypass valve to reach the maximum opening degree.

8. The open-circuit purging method for a fuel cell system according to claim 4, wherein, The fuel cell system further includes a thermal management subsystem, which includes a temperature control valve, a water pump, and a heat dissipation device. After purging the components of the hydrogen subsystem and the air subsystem according to the third target value, the method further includes: Control the opening degree of the temperature control valve to reach the maximum opening degree; The speed of the water pump is controlled to be the rated speed of the water pump; and, The speed of the cooling fan is controlled to be the rated speed of the cooling fan.

9. An open-circuit purging device for a fuel cell system, comprising a processor and a memory, the memory storing computer program instructions executable by the processor, wherein the processor, when executing the computer program instructions, implements the steps of the method as described in any one of claims 1 to 8.

10. A computer-readable storage medium comprising computer program instructions stored thereon, which, when executed by a processor, cause the processor to perform the steps of the method as claimed in any one of claims 1 to 8.

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